Spray polyurethane foams (SPFs) are often formed by combining an isocyanate-reactive component and a polyisocyanate in the presence of water and a physical blowing agent. Aromatic polyester polyols and/or sucrose-based polyether polyols are often used in the polyol component. Such polyols are often selected for SPF applications, such as wall or roof insulation applications, because of the fire resistance properties they tend to impart to the foam.
Historically, the physical blowing agents used in SPFs have often been chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). CFCs and HCFCs are, however, becoming disfavored because of their ozone depletion potential and relatively high global warming potential. As a result, alternative physical blowing agents are under consideration.
One class of alternative physical blowing agents with low or no ozone depletion potential and low global warming potential are certain halogenated olefins, such as fluoroolefins, that include at least one halogen, such as fluorine, and at least one carbon-carbon double bond. Some of these fluoroolefins also include hydrogen and at least one chlorine atom and, as a result, are sometimes referred to as hydrochlorofluoroolefins or HFCOs.
Phase stability of the isocyanate-reactive component is particularly important for SPFs, because phase instability resulting in any precipitates or deposits can cause equipment damage. In addition, phase instability can lead to metering accuracy problems during the spray application process which can affect the stoichiometry of the resulting polyurethane spray system, resulting in poor reactivity and poor foam performance properties.
As a result, it would be desirable to provide polyurethane foam-forming compositions with a phase stable isocyanate-reactive composition that includes a halogenated olefin blowing agent that has low or no ozone depletion potential and low global warming potential, such polyurethane foam-forming compositions being suitable for spray application to produce polyurethane foams with good fire resistance properties, low smoke generation, and low or no scorch due to reduced exotherm, thereby making them particularly suitable for use, for example, as relatively thick wall and/or roof insulation.
The present invention was made in view of the foregoing desire.